The present invention relates in general to an energy transfer device and in particular to an energy transfer device for use in a desulfurizing plant including a first heat exchanger arranged in a stream of crude gas flowing to a scrubber, a second heat exchanger arranged in a stream of clean gas behind the scrubber, the first and second heat exchangers including heat exchange pipes and being interconnected by transfer conduits for a forcibly circulating heat carrying medium, the heat exchanging pipes and the transfer conduits being made of a pressure resistant material, such as steel.
In the course of an intensified effort to protect environment, both the newly constructed power plants as well as existing power plants must take precaution for desulfurizing flue gas. The desulfurizing process takes place principally in wet desulfurizing systems in which the flue gases in the cleaning process are cooled by a scrubbing solution so long until the gas leaves the scrubber at a temperature of about 50.degree. C.
Thereafter, however, it is necessary that the cleaned flue gas be again heated to a temperature of at least 72.degree. C. before it is released in the atmosphere. For this reheating, different methods are developed. The most energy saving reheating methods are those in which the heat energy required for the reheating is withdrawn from the hot crude gas to be cleaned.
For this purpose a heat exchanger with ribbed heat exchanging pipes has been installed in the stream of crude gas before the scrubber and this heat exchanger is connected via a heat carrying fluid such as for example water mixed with an antifreeze medium, in a second heat exchanger also provided with ribbed heat exchanging pipes arranged in the stream of clean gas behind the scrubber. By means of this reheating device it is possible to withdraw heat from the crude gas stream and to transfer the heat energy via the heat carrying medium into the clean gas stream. As a rule, the pipes and heat medium transfer conduits for such heat exchangers are made of steel. Such a construction however encounters considerable difficulties in the case when temperature is in the range of the dew point of sulfuric acid. It has been already proposed to provide the individual parts of the heat exchangers with coatings. It has been found however that due to large molecule structure of the coating material in the course of time residues of diffused molecules are formed below the coating and destroy the base material and loosen the coating. Known is also the application of enameled heat exchangers employed in connection with flue gas desulfurizing installations. Nevertheless even this measure, for various reasons has not been found as satisfactory.